The present invention relates to a scanning probe and a scanning endoscope configured to scan on a target with light by causing a tip of an ultrathin optical fiber to oscillate to obtain image information of the target, and to an objective lens suitable for such a scanning probe and a scanning endoscope.
Electronic-scopes have been used by doctors as medical apparatuses for diagnosis on a body cavity of a patient. A tip part of an electronic-scope of this type is configured to be compact in size so that an insertion unit of the electronic-scope can be smoothly inserted into the body cavity of the patient. At the tip part of the electronic-scope, various types of components are installed. In practical, the design minimum outer diameter of the tip part of the electronic-scope is defined by components having larger sizes in the tip part (e.g., a solid state imaging device). Therefore, in order to thin the tip part of the electronic-scope, it is desirable to employ a further downsized solid state imaging device. However, in general as the size of a solid state imaging device decreases, the performance of the solid state imaging device, such as a resolution, a dynamic range, and an SN ratio, deteriorates. Therefore, even if the tip part of the electronic-scope is thinned, it is not appropriate to employ such a downsized solid state imaging device without careful consideration.
A scanning probe configured to be thinner than a conventional electronic-scope (i.e., an electronic-scope employing a solid state imaging device) by employing a configuration not requiring use of a solid state imaging device has been proposed. A medical observation system having a scanning probe of this type is disclosed for example in U.S. Pat. No. 6,856,712 (hereafter, referred to as U.S. Pat. No. 6,856,712). The scanning probe disclosed in U.S. Pat. No. 6,856,712 is configured to scan on a target with scanning light produced by causing a tip of a single optical fiber to oscillate so that the target is scanned with a predetermined scanning pattern. The scanning probe detects reflected light from the target and executes photoelectric conversion to output sequentially a converted signal to a video processor. The video processor processes the received signal to display an image of the target on a monitor. A doctor is able to conduct diagnosis and treatment while observing the image of the target on the monitor.